The present invention relates to heat sink plate mountings and more particularly, to a mounting for a flat faced heat sink plate against which a flat faced heated body is placed such as is used in an electrophoresis unit.
There are many situations where it is required to withdraw heat from a flat surfaced body to a heat sink so as to avoid heat damage either to the body or to a component within or attached to the body. In some of the situations, the heat sink is provided as an element having a flat surface which is placed in contact with the heated body flat surface.
In this particular situation, it is not unusual that complete face-to-face contact between the two is not achieved over the expanse of each so that in consequence and while measurable heat exchange occurs between the heated body and the heat sink component, uniformity of heat transfer is not present over the contact area of the two elements. The result is creation of hot spots in some locations of interface contact.
Use of a flat heat sink plate in face-to face contact with a flat heated body is practiced in a process for the electrophoretic separation of DNA or RNA. Electrophoresis is a well known molecular biological art practice. An explanation of the practice is found, e.g., in the Background of the Invention description of U.S. Pat. No. 5,324,412.
In the electrophoresis process, a polymerized gel slab is sandwiched between two flat glass or plastic plates, the sandwich is mounted in the electrophoresis unit with its upper and lower ends in contact with electrolyte solutions in respective unit upper and lower reservoirs, a biological sample from which molecules are to be separated is introduced at the top of the gel, and an electric potential is established between the upper and lower reservoir electrolytes.
This results in migration of molecules from the sample through the gel slab from top to bottom, separated molecules becoming visibly discernible in the slab in the course of processing. Ideally, the molecule presence will appear as vertically and horizontally aligned dashed or dotted lines.
In the course of processing heat will be generated in the slab so that heat carry off should be made, this being done by face-to-face engaging one sandwich plate with a heat sink plate. Desirably, heat carry off from the gel slab should be uniform across the slab so that heat condition in the slab would be uniform. Further, if effective uniform heat removal from the slab is present, the slab can be allowed to run hotter since such makes the processing faster.
If pockets of hot or cold spots are created in the slab because there are correspondingly different heat conditions of heat transfer from the slab to the heat sink plate at these locations, the molecule migration speed through the slab will be affected and in consequence, the alignment and more particularly the horizontal alignment of molecule presence is distorted causing so called "smile" and "frown" appearances of the line depictions of the separated molecules which burdens the scientist with trying to correctly match the line or dot associations.
Lack of uniform heat transfer happens because there is lack of uniform face-to-face contact between the respective planar faces of the sandwich plate and the heat sink plate. This can be caused by unequal clamping effect applied to the gel slab sandwich when it is mounted in the electrophoresis unit with clamps, clamps being carried on the unit to clampingly engage the sandwich at side margins of the sandwich. Also, the clamping of the sandwich can make the gel slab thinner at the sides and thicker in the middle so that this can cause heat transfer problems as can warping of the glass plates caused by excessive clamping force and with warping, plate contact with the heat sink plate is reduced.
Clamping of the plate in mounted position is also effected to insure a tight sealing of an upper part of the sandwich against a seal member carried on the unit just adjacent below an edge of an opening in the upper reservoir at which the electrolyte in the upper reservoir is placed in communication with the gel slab, a requirement of the processing. Without a proper such sealing, electrolyte from the upper reservoir could leak out and possibly drip down the sandwich to the lower reservoir wherein it could cause thwarting of the processing.
In an effort to overcome the disadvantages noted above, it is known to attach the heat sink plate to a wall support therefor with interposed elastic links such as rubber plates so that the heat sink plate has some floating movement thought to improve making face-to-face contact between the two better. This practice has not been fully successful. It is difficult with these pads to strike a balance between making full face-to-face contact on the one hand and a proper engagement of the upper reservoir/sandwich plate seal so that if better heat transfer is made more uniform with better plate contact, improper sealing of the reservoir with the sandwich results. If greater clamping pressure is applied to the gel sandwich in quest to seal the reservoir, the sandwich glass easily can be bowed so that the leak potential is magnified in addition to the adverse effect it can have on uniform heat transfer.
Accordingly, it is desirable that an improved mounting for a heat sink plate of an electrophoresis unit be provided so that maximized face-to-face contact of the planar face of the heat sink plate with a sandwich plate of the gel slab sandwich exist while at the same time a sure sealing of the gel slab sandwich with the unit upper reservoir also be present and that the same be made without need for an unusually high clamping force.